Joe is having a party. He is not a guest at his own party. On the first doorbell ring, 1 guest enters. On the second doorbell ring, 2 more guests enter. On the third ring, 3 more guests enter, and the pattern continues. How many guest are at the party after the 200th ring?
2006-10-08 09:55:06 · 11 answers · asked by jkelly 2 in Science & Mathematics ➔ Mathematics
try it with a checker board its only 64 spaces, have fun
2006-10-08 09:58:41 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Let B = bell and B1 = doorbell 1, B2 = doorbell 2, etc. Okay?
I found that 50 people showed up between B1 and B10 simply by adding.
Le me do three with you.
B11 = 11 people
B12 = 12 people
B13 = 13 people and so forth.
50 people showed up at the party after the first 10 rings, right?
I will now add 11 + 12 + 13 to 50 = 86.
Do you see the pattern? Each doorbell indicates the number of people that showed up at the party.
It is now your job to find the rest of the people who came to the party after 200 doorbell rings. Remember, since I found 86 after the 13th ring, you must add your total to mine in order to find the grand total of people who came to the party after the 200th ring.
My answer of 86 + your total = grand total.
I hope this helps.
Guido
2006-10-08 17:12:44 · answer #2 · answered by Anonymous · 0⤊ 0⤋
You should get an invite to Joe's party then you could count the number of guests.
2006-10-08 17:02:57 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Use the formula
1+2+3+...+n = n(n+1)/2,
with n=200. You get 200(201)/2=20,100.
2006-10-08 16:57:45 · answer #4 · answered by James L 5 · 0⤊ 0⤋
1+2+...+200 =200*201/2=20100
2006-10-08 17:06:06 · answer #5 · answered by rwbblb46 4 · 0⤊ 0⤋
The sum of the first n numbers is n(n+1)/2 so if n - 200 there are 20,100 people at the party.
This is one *hell* of a blow-out!! How come *I* wasn't invited? âº
Doug
2006-10-08 16:59:56 · answer #6 · answered by doug_donaghue 7 · 0⤊ 0⤋
g=1+2+3+4.....+199+200
g=200*(201)/2=20100 guests.
I hope he has a REALLY big house! :)
2006-10-11 23:40:35 · answer #7 · answered by yupchagee 7 · 0⤊ 0⤋
1+2+...+200=(200)(201)/2
=20100
2006-10-08 16:57:32 · answer #8 · answered by mathematician 7 · 0⤊ 0⤋
201/2=100.5
200*100.5= 20100 people
2006-10-08 16:58:26 · answer #9 · answered by bruinfan 7 · 0⤊ 0⤋
That's a lot of guests that's for sure. I'd go with the answers above me. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2006-10-08 17:02:35 · answer #10 · answered by Snuz 4 · 0⤊ 0⤋